June 12, 2024 - Alaska's Yukon Delta - True and False


True Color False Color

The Yukon Delta and nearby Bearing Sea were filled with sediment on June 9, 2024, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this true-color image of the springtime scene. Melting snow and ice have over-filled the Yukon River and nearby rivers, causing them to spill their banks. The expansive and rushing waters capture sediment as they move from the inland regions of Alaska and Canada and ultimately deposit it in the Yukon Delta and the Bering Sea.

The true-color image, which uses visible light (bands 1,4, and 3), shows the scene very much like our eyes would see it. The Delta appears densely painted in browns and tans, and dramatically demonstrates the movement of sediment in the springtime.

While true-color images are quite useful, sometimes scientists want to see different detail, such as being able to separate out water from vegetated land. For this they can turn to “false-color” images. One type of false-color image uses both infrared and visible light (bands 7,2,1) to create a vastly different view of the same scene than seen in true-color. In this type of image, vegetation appears bright green; water looks blue, with deeper water appearing darker blue; ice and snow (frozen water) shows up as bright electric blue; open land, mud, or dead vegetation looks brown or tan; and clouds usually appear white although high, cold cloud that contains ice crystals may be tinted with electric blue. Sediment suspended in water appears primarily as it affects depth of the water, so thick sediment near the surface gives the appearance of more shallow water and may look light blue while lesser amounts of sediment suspended in moving rivers may not change the color of the river to a great extent.

To view the difference between the true-color image (1,4,3) and false-color image (7,2,1) of the Yukon Delta captured by Terra MODIS on June 9, 2024, simply click on the appropriate labels. The false-color image reveals a much more detailed look at the region. Vegetation is widespread and cut by the wide and winding Yukon River as well as multiple channels through the Yukon Delta. The marshlands of the Delta are tinted with tan, suggesting sediment, open land, and/or senescent vegetation. Dark blue speckles and circles mark widespread thermokarst lakes, especially south of the Delta and faint washes of electric blue give evidence that snow or ice remains on the higher elevations in the region. The extremely heavy sediment floating in the true-color image is barely visible as light blue tones off the coast.

Image Facts
Satellite: Terra
Date Acquired: 6/9/2024
Resolutions: 1km (47.1 KB), 500m (102.2 KB), 250m (232.9 KB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC